OP0153 DEVELOPMENT OF A PROVISIONAL SELF-REPORTED DEFINITION FOR ACUTE CALCIUM PYROPHOSPHATE CRYSTAL ARTHRITIS: PRELIMINARY RESULTS OF A MULTICENTRE STUDY
Authors: E. Cipolletta, M. Andrés, S. Ottaviani, T. Pascart, I. Calabuig, S. Gomez-Sabater, R. Caño-Alameda, B. Leger, A. Pacaud, E. Moscioni, P. Muto, V. Caira, C. Bruno, D. Rozza, G. Carrara, A. Zanetti, A. Abhishek, E. Filippucci
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Acute calcium pyrophosphate (CPP) crystal arthritis is a common clinical presentation of CPP deposition (CPPD) disease, and recurrent episodes occur in 25% of patients with CPPD disease <sup>[1]</sup>. Although recent studies have evaluated the short-term efficacy of different drugs in acute CPP crystal arthritis <sup>[2-4]</sup>, future studies would focus on reducing the frequency of these episodes in the long-term. <h3>Objectives</h3> To develop a patient-reported definition for acute CPP crystal arthritis in patients with CPPD disease. <h3>Methods</h3> Consecutive patients with a crystal-proven diagnosis of CPPD disease were enrolled in a cross-sectional study during routine inpatient and outpatient clinical care at five centres from France, Italy, and Spain. Patient-reported questions on the features of acute CPP crystal arthritis as per the OMERACT CPPD Working Group were evaluated by a rheumatologist <sup>[5]</sup>. The opinion of a second expert rheumatologist was the gold standard. Synovial fluid (SF) leukocyte count &gt;2,000 cells/mcl was the reference standard in a sensitivity analysis. Definitions based on the number of criteria independently associated with acute CPP crystal arthritis and classification and regression tree approaches were developed. <h3>Results</h3> Data for 164 patients with CPPD disease were included. Their mean age was 71.8 years (SD 10.7 years), 104 (63.4%) were female. At the time of the assessment, 60/164 (36.6%) participants had acute CPP crystal arthritis, 25 (15.2%) had chronic inflammatory CPP crystal arthritis and 79 (48.2%) OA+CPPD according to the experts. SF was available in 44/164 (26.8%) participants, and 24/44 (54.6%) had a leukocyte count &gt;2,000 cells/mcl in the SF. Patient-reported warm joint, patient-reported swollen joint, time from the pain-onset to-peak-pain (&lt;48 hours), and patient-reported acute CPP crystal inflammatory arthritis were independently associated with the reference standard in multivariate analysis (Table 1). The greatest discriminating power was noted for the presence of 3 or more of the above 4 criteria [sensitivity 86.7% (95%CI: 75.4%-94.1%) and specificity 88.5% (95%CI: 80.7%-93.9%)] in the main analysis. The sensitivity and specificity of this definition using the SF as the gold standard were 83.3% (62.6%-95.3%) and 85.0% (62.1%-96.8%) (Figure 1). A classification tree identified patient-reported warm joint, followed by patient-reported inflammatory arthritis as the most informative variables for identifying acute CPP crystal arthritis [sensitivity 80.0% (95%CI:67.7%-89.2%) and specificity 90.4% (95%CI:83.0%-95.3%)]. <h3>Conclusion</h3> Provisional self-reported definitions for acute CPP crystal arthritis in patients with CPPD were developed. The next step in the development of these criteria will be external validation. <h3>References</h3> [1] Yates KA, et al. J Rheumatol. 2020;47:1261-6 [2] Dumusc A, et al. Joint Bone Spine. 2021;88:105088 [3] www.clinicaltrials.gov/ct2/show/NCT03128905 [4] Cipolletta E, et al. Clin Exp Rheumatol. 2020;38:1001-7 [5] Fuller A, et al. Semin Arthritis Rheum. 2021;51:650-4 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.